The present invention relates generally to avionics for aircraft and more specifically to airborne collision avoidance systems and transponders.
The development of an effective airborne collision avoidance system (CAS) has been the goal of the aviation community for many years. Airborne collision avoidance systems provide protection from collisions with other aircraft and are independent of ground based air traffic control.
Spurred by the collision of two airliners over the Grand Canyon in 1956, the airlines initiated a study of collision avoidance concepts. A chronology of the development of airborne collision avoidance systems can be found in "INTRODUCTION TO TCAS II", printed by the Federal Aviation Administration (FAA) of the U.S. Department of Transportation, March 1990, which is incorporated herein by reference.
By the late 1980's a system for airborne collision avoidance was developed with the cooperation of the airlines, the aviation industry, and the FAA. The system, called Traffic Alert and Collision Avoidance System II (TCAS II) was mandated by Congress to be installed on most commercial aircraft flying in U.S. airspace by the early 1990's.
A TCAS II equipped aircraft monitors other aircraft within approximately a 20 mile radius of the TCAS II equipped aircraft. When an intruding aircraft is determined to be a threat the TCAS II system alerts the pilot to the danger and gives the pilot bearing and distance to the intruding aircraft. If the threat is not resolved and a collision or near miss is probable the TCAS II system advises the pilot to take evasive action by either climbing or descending to avoid a collision.
Although current collision avoidance systems (CAS) such as TCAS work well, improved performance and functionality have been proposed. Specifically, the FAA would like to extend the range of CAS systems from 20 miles to 40 miles or more. It has been proposed that an extended range CAS would make flying safer and provide other benefits such as enabling aircraft to perform self-initiated air traffic control (ATC) functions over the ocean. This would allow faster aircraft to pass slower aircraft on their own during long oceanic flights, a maneuver not currently permitted. This would save both time and fuel for aircraft.
The problem is that an extended range CAS system must be compatible with currently operating CAS systems which do not have extended range capability. This implies that extended range systems must substantially increase their range of transmission and reception to be capable of communicating with a non-extended range equipped CAS aircraft. The only obvious solutions are expensive hardware upgrades to dramatically improve both the transmitter and/or receiver performance of the system. These solutions require expensive redesigns of the entire system.
Significant cost savings would be achieved by a collision avoidance system which achieves extended range without the need for expensive hardware designs. It would be especially useful if the range of CAS systems could be improved while maintaining compatibility with current systems.
Clearly there exists the need for an airborne collision avoidance system which achieves extended range, makes flying safer, saves time and fuel, is backward compatible, and achieves these goals with minimum expense.